O2086: Multisystem inflammatory syndrome in children in the United States in 2022

Background: Multisystem inflammatory syndrome in children (MIS-C) is a hyperinflammatory disorder that emerged during the COVID-19 pandemic. A study using the National Inpatient Sample database (doi.org/10.5114/reum/189213) reported that 2,790 children were hospitalized with MIS-C in 2021 in the United States. We aimed to describe the epidemiology and outcome of MIS-C during 2022 to determine the effect of new variants of COVID-19 that spread during 2022, COVID-19 immunization, and changes in COVID-19 treatment practices.

Methods: A retrospective cross-sectional analysis using the Kids’ Inpatient Database was performed for hospitalized children in 2022. Neonates were excluded from the analysis. ICD-10 codes were used to identify children with MISC. Demographics and clinical outcomes were compared in patients with and without MIS-C. Chi-square, Mann-Whitney U, and regression analyses were performed for inferential statistics.

Results: Among 1,966,893 hospitalized children, there were 94,042 (4.8%) children with a COVID-19 diagnosis and 6,911 (0.35%) children with a diagnosis of MIS-C. The demographic and clinical characteristics in MIS-C and all other discharges are presented in Table 1. The median age of children hospitalized with MIS-C was 10 years (IQR 4-16, P< 0.001). MIS-C was more common in male, Hispanic, and obese children and was more frequently reported in the first quarter of 2022 (50.9%). The peak prevalence of MIS-C followed the peak of COVID-19 admissions (Figure 1). The Northeast region represented disproportionally higher MIS-C admissions. Compared to children without MIS-C, sepsis (8.2% vs 0.9%, P < 0.001), acute liver failure (ALF; 1.9% vs 0.2% P < 0.001), acute renal failure (ARF; 16% vs 3%, P < 0.001), acute myocarditis (39.7% vs 0.003%; p< 0.001), cardiac arrhythmias (7.9% vs 1.21%, P< 0.001), ARDS (1.8% vs 0.2%, P < 0.001), invasive mechanical ventilation (IMV; 8.3% vs 3.1%; p< 0.001), thrombocytopenia (15.5% vs 1.7%, P < 0.001) and DIC (1.7% vs 0.1%, P < 0.001) were more prevalent in children with MIS-C. The use of IVIG was documented in 24.7% of patients with MIS-C. The median length of stay was 4 days (IQR 2-6 days, P < 0.001), and the median charges of patients admitted with MIS-C were $64,327 (IQR 35,295-127,293, P < 0.001). The mortality rate was 1.78% in children with MIS-C. On regression analysis, the mortality was higher with IMV (OR:11.3), DIC (OR:3.49), ALF (OR:3.32), myocarditis (OR:2.66), ARF (OR:2.42), and sepsis (OR:1.7).

Conclusion: The study describes the largest cohort and presents the national prevalence and demographic characteristics of children hospitalized with MIS-C in the United States in 2022. MIS-C is often associated with organ dysfunction. Hospital admissions for MIS-C peaked following the surge in COVID-related hospitalizations. Although the COVID-19 pandemic has subsided, examining the national epidemiology of MIS-C in relation to COVID-19 remains important both for historical context and future public health considerations.